1. Field of the Invention
This invention relates to improvements in a front suspension for a vehicle which suspension is of the type having both characteristics of a double wishbone type suspension and of a strut type suspension, and more particularly to a structure for installing a stabilizer bar to the front suspension of this type.
2. Description of the Prior Art
A vehicle front suspension of the type having both characteristic of a double wishbone type suspension and of a strut type suspension has been proposed by the same group including the inventors of the present invention and disclosed in a co-pending U.S. patent application Ser. No. 08/716,064, entitled "Front Suspension Device". This front suspension is arranged as follows: A rotational joint is disposed on the upper section of a steering knuckle for rotatably supporting a front wheel. The rotational joint includes a rotatable member which is rotatable around an imaginary axis of the rotational joint which axis extends generally vertical. A shock absorber is provided in such a manner that the lower section thereof is installed to the rotatable member of the rotational joint. An upper link is disposed to extend generally in a vehicle width direction, in which one end section thereof is connected to a vehicle body-side member while the other end section thereof is pivotally connected to the movable member of the rotational joint. A lower link is provided to extend in the vehicle width direction so as to connect the lower section of the steering knuckle and the vehicle body-side member. Additionally, the one end section of the upper link is connected at its single installation position to the vehicle body-side so as to form a connector, while the other end section of the upper link is connected at its single installation position to the movable member of the rotational joint so as to form a connector. Here, the upper link is arranged such that an imaginary axis connecting the centers of the both connectors crosses the axis of the rotational joint.
In general, a front suspension is provided with a stabilizer bar for the purpose of suppressing roll of a vehicle during turning of the vehicle. The stabilizer bar extends in the vehicle width direction and is supported at its central section to a vehicle body-side member such as a suspension member. Each of the opposite end sections or wheel-side installation sections of the stabilizer bar is connected to a part of the front suspension. For example, in a front suspension of the strut type or the double wishbone type, each wheel-side installation section is connected to a lower link or the like of the suspension.
However, the above-discussed front suspension has been newly developed and proposed, and therefore a suitable arrangement for installing the stabilizer bar to the front suspension has not yet been disclosed. Assume that the wheel-side installation section of the stabilizer bar is connected to the lower link of the front suspension similarly to in conventional front suspensions. In this case, if a stabilizer reaction force in a vertical direction is input to the lower link during turning of the vehicle, the camber angle of the front wheel cannot be changed under the action of the stabilizer reaction force. In other words, the stabilizer bar provides no effect to a camber angle change in the front wheel during the turning of the vehicle.
Otherwise, in case that the wheel-side installation section of the stabilizer bar is connected to the inside section of the steering knuckle, it can be made possible that the camber angle of the outside wheel in a vehicle turn is slightly changed into a negative direction by an amount corresponding to the yield of an elastomeric bushing disposed at the installation section of suspension links. In view of this, it may be proposed to lower the rigidity of the elastomeric bushing. However, if the rigidity of the elastomeric bushing is set to be low in the conventional suspensions, difficulties are encountered in the suspension such that, for example, the wheel alignment stiffness cannot be maintained at a suitable level. For such reasons, it has been difficult to optimize both the rigidity of the elastomeric bushing and the camber angle change during the vehicle turn. In other words, lowering the rigidity of the elastomeric bushing will reduce the amount of the camber angle change in a negative direction under the action of the stabilizer reaction force.